Food security and energy for transportation are global concerns due to increased population and decreased fossil fuel resources. Countries that produce and export oil are not even safe from the depletion of oil and the socioeconomic consequences. Land crops are an alternative to fossil fuels and are a source of oil for biofuels like bioethanol, biodiesel and jet fuels. However, many other market segments, such as human and animal nutrition, also use land crops as a source of raw materials. Unfortunately, land surface for agriculture is diminishing, while global population is growing. Global population is estimated to be around 9.3 billion in 2025. Growing worldwide populations are expected to increase food and energy demand (Wheeler and von Braun, 2013). But land crops cannot respond to both increased energy and food demand in the future. Lobell et al. (2008) reported that south Asia and southern Africa are two regions that will be negatively impacted by climate change and will likely suffer from decreased production before crops can adapt. Moreover, the demand for biodiesel results in an increase of land crops for energy production (Panichelli et al., 2015). A major challenge to global food and energy security is global population growth and the use of land crops for renewable energy (Lele et al., 2013). A source of energy that is non-competitive with food is feasible and more sustainable, both are necessary for worldwide acceptance.
Microalgae is a non-competitive alternative that will complement land crops and has the potential to alleviate concerns about energy and food security. Microalgae can play a significant role in climate change mitigation without any potential conflicts with food security. Microalgae is a source of food and renewable energy. Microalgae biomass can be produced in any country that has fresh or salt water. Land which is not suitable for agriculture can produce microalgae biomass, it is the only crop producible using salt, brackish wastewater and non-arable land. Microalgae is a micro-crop, it grows fast and yields 50 times more biomass than any other land crop. Microalgae cells use sun light to convert CO2 into chemical energy. It has the potential to accumulate over 50% (DW) of oil. Microalgae biorefineries will significantly impact socioeconomic development and simultaneously solve problems in both bioenergy and food security. Thus, microalgae is a sustainable means to overcome global food, energy, environment and socioeconomic concerns.
Microalgae biomass is a potential feedstock for production of sustainable biofuels and nutraceuticals. Microalgae biorefineries produce biochemicals with health benefits. Many chemicals can be extracted from microalgae biomass including oil for biofuels, omega-3/6/9 oil, water-soluble chemicals, carotenoids, proteins, and polysaccharides. Animal feed is also produced from the microalgae biomass. Production of biofuels is a national interest due to food and energy concerns. The microalgae industry will benefit society and the economy by solving problems in food and energy.
However, it has been reported that it is not yet commercially feasible to produce biofuels via microalgae as feedstock (Demirbas, 2011; Rawat et al., 2013; Stephens et al., 2010). The design of the microalgae biorefinery should involve high-value chemicals production and reduce capital investment and operating expenses.
The Microalgal Biorefinery
The microalgae biorefinery utilizes a multistep process including biomass production, harvesting, drying, oil extraction, and further processing of residual biomass. Many biomass production technologies have been reported (Elser et al. 2017). There are open and closed systems, mainly including open pond (Chisti, 2010), photobioreactor, and fermenter (Oncel and Kose, 2014) respectively. Recently, combinations of two production systems have been reported, such as a photobioreactor-open pond, fermenter-photobioreactor, or fermenter-open pond (Moody et al., 2014; Rawat et al., 2013). Generally, the open pond method utilizes a raceway pond in a closed-up channel with an oval shape, open to the air. The pond is mixed with a paddle and the water is 0.20 to 0.4 m deep. Photobioreactor (PBR) and fermenter are tools to produce biomass under controlled conditions. PBR uses sunlight alone or both sunlight and organic carbon, whereas the fermenter only uses organic carbon as the source of energy.
Biomass harvesting is the second step in the microalgae biorefinery process. After a period of microalgae growth, the biomass concentration is high enough to create a shading effect, which can impact light efficiency and biomass yield. The biomass is harvested using physical or chemical tools. The physical harvesting involves centrifugation, sedimentation, filtration, chemical flocculation, or bio-flocculation (Brennan et al., 2010; Bilad et al., 2012). Chemical flocculation is performed using pH adjustment and metal ions such as Fe3+ or Mg2+ (Brennan et al., 2010; Yang et al., 2011; Sharma et al., 2013). Some processing technology requirements require drying the biomass before extraction. Pre-treatment of harvested biomass is an extra step which can increase product content and improve processing yield.
The extraction of end products is the last step in the biorefinery process. This process can be performed using wet or dried biomass. Biomass processing involves destructive and non-destructive techniques. A milking process is the extraction of oil by non-destructive techniques, it allows for continuous biomass growth and in some cases continuous milking (Ramachandra et al., 2009). Destructive oil extraction is the most used in the laboratory, pilot and commercial scale (Wang and Yuan, 2014, Ranjith et al. 2015). Destructive extraction of oil and other compounds uses both wet and dried biomass (Lee et al., 2009, Rodolfi et al., 2009). It involves a disruption of the cell wall and the membrane by solvent and/or physical means (Halim et al., 2012; Bligh & Dryer 1959; Patil et al., 2011). Commercial processors most often use hexane as the solvent and recycle it by distillation. Extracted oils are used as a commodity or converted to biofuel. Transesterification of the extracted oils produces biodiesel. Catalytic cracking of the extracted oils produces aircrafts fuel. By-products can also be extracted with further processing. Moreover, residual microalgae biomass after oil extraction can be used as animal and fish feed, which makes algae a valuable input for livestock and aquaculture industry.
Capital investment and operation expenses are the main constraints when starting a biorefinery. Fiscally breaking even is the first critical step in the economics of the biorefinery, the second step is generating positive cash flow. Biomass production and processing are cost-challenging steps in the initial expenditure phase. Chisti (2010) reported that sustainable microalgae biofuel production depends on cutting the actual cost by 10 times. Commercial biorefineries need to minimize capital and operation costs and maximize the yield of by-products. In order for the microalgae industry to be commercially feasible, it is necessary to reduce the expenditure in biomass production and its processing and increase sales of high value by-products also called high-value chemicals. By-products mainly include proteins, polysaccharides, omega-3, carotenoids compounds and biofuels. It is well known that these natural products provide high nutritive values with health care benefits. Thus, they have wide support from the academic community, nutritionists and consumers (Privadarshani et al., 2012; Ali & Saleh, 2012). High-value by-products are the main source of cash flow. They can be an exit strategy toward a feasible commercial biorefinery.
High-Value Chemicals
Microalgae is a sustainable natural feedstock. Microalgae is a source of bioactive compounds such as fatty acids, proteins, polyphenols, carotenoids, vitamins, and polysaccharides. These compounds have potential applications in pharmaceutical, nutraceutical, food, drinks, animal feed, bioenergy and cosmetic fields.
Proteins and Fatty Acids
Many studies have shown that microalgae strains are rich in polyunsaturated fatty acids (PUFAs), polyphenol, and carotenoids (Herrero et al, 2013, Eom & Kim 2012). Spirulina is a model of the commercial application to the algae biomass industry. Spirulina platensis is generally served as a supplement for its protein content and other bioactive components. Spirulina is rich in proteins (55% to 70%) (Ouhtit et al., 2014, Ali & Saleh, 2012). Food supplements can utilize protein directly from whole algae cells or after extraction. Microalgae meal is easy to dry after oil extraction, it can be stored at room temperature, and it is rich in proteins and other beneficial health components.
Essential fatty acids are not synthesized by the human body and must be provided in the diet. These fatty acids include alpha-linolenic acid (ALA), linoleic acid (LA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The Mediterranean diet is rich in ALA, and populations who are using the Mediterranean diet are more resistant to cardiovascular disease (Simopoulos, 2008). Rabinovitz et al. showed the importance of LA/ALA ratio in the diet (Rabinovitz et al., 2004). Djoussé et al. (2003) reported an association between ALA consumption and a lower risk of carotid atherosclerosis.
Polysaccharides
There are water-soluble and insoluble polysaccharides groups. Generally, soluble polysaccharides include hemicellulose, pectin, gum, β-glucan and novel fibers. Insoluble fibers include cellulose, lignin, chitin, chitosan and some hemicellulose. Insoluble fibers are known by the decrease of the transit time through the gastrointestinal system, the increase of the fecal bulk, and it is associated with increased secretion of bile acids (Brouns et al., 2002). Water-soluble fibers are known by an increase of the transit time and a delay in gastric emptying.
Macroalgal polysaccharides include agar, carrageenan, and alginate. They are easily isolated from macroalgae because of their ability to bind water, form a gel, and to form and stabilize emulsions. The development of viscous gels depends on the concentration of soluble fibers, and their structure and viscosity properties. Macroalgal polysaccharides are used as stabilizers, water-thickeners, emulsifiers, and gelling agents in food, beverages, pharmaceutical, cosmetics, paper, and textiles industries (Milani et al., 2012; de Jesus Raposo et al., 2015).
Seaweed (aka macroalgae) has shown that it is a sustainable source of polysaccharides, and the global market is well developed with many commercial applications. The macroalgal polysaccharide market is a $1 billion USD industry including alginate, agar, and carrageenan (Burtin 2003). The whole macroalgal industry offers a variety of products with a total annual production value of about $6 billion USD, including $5 billion as products for human consumption. For example, the price of pharmaceutical grade alginate is $13.00 to $15.50 per kg and food grade is $6.50 to $11.00 per kg. Unfortunately, the microalgae polysaccharide industry is not as developed. The main key factor in future developments in the commercial microalgal polysaccharide industry is the feasibility of biomass production and the polysaccharide extraction process.
It has been reported that total polysaccharides content of seaweeds can reach 75% of the dry weight, which is higher than the fiber content of most fruits and vegetables (Jimenez-Escrig and Sanchez-Muniz, 2000). The cell wall is built mainly with cellulose, hemicellulose and neutral polysaccharides in order to support the tall structure in water (Gómez-Ordóñez et al., 2010). The structure of the cell wall in seaweed is less rigid than in the land crops and microalgae, which make the polysaccharides easier to extract. Seaweed polysaccharides are generally involved in food, beverages, pharmaceutical and nutraceutical industry. Macroalgae polysaccharides are species specific. Green algae contain starch, xylan, mannan, ionic polysaccharides, sulphuric acid polysaccharides, and sulphated galactans (Zaporozhets et al., 2014). Red algae contain agar, carrageenan, xylan, floridean starch, water-soluble sulphated galactan, and porphyran as mucopolysaccharides (Kraan, 2012). Brown algae are known for their content in alginates, fucan, laminaran, and sargassan (Bocanegra et al., 2009).
Macroalgae biomass and products have been used for many centuries as food and in traditional medicine. Many studies report the association between consuming macroalgae products, and a health benefit (Lovegrove et al., 2017; Hamed et al., 2015; Costa et al., 2010). Macroalgae fibers are anionic polysaccharides; some are only a little fermented and others are not fermented by human gut microbiota (Fåk et al., 2015). One study showed that fibers from macroalgae are less fermented and produce less short chain fatty acids (SCFA) than those from plants (Murata & Nakazoe, 2001).
Algal polysaccharides are known by their broad bioactive properties. Many viscous-soluble polysaccharides have been correlated with hypocholesterolemic and hypoglycemic effects. While water-insoluble polysaccharides, mainly cellulose, have been reported to be associated with a decrease of the digestive tract transit time (Holdt & Kraan 2011). Fucoidans, aka sulfated polysaccharides, are involved extensively in the cell walls of brown macroalgae. In addition to the impact on the inflammatory and immune systems, fucoidans demonstrated many physiological and biological features, such as antitumor, anticoagulant, antioxidant, antiviral, and antithrombotic activities (Wijesekara et al., 2011). Fucoidan has gelling properties, and it has been used as a dietary complement as well as an antioxidant (Heim et al., 2014). Porphyran, another sulfated polysaccharide, is the major component of the red macroalgae Porphyra. As a second main source of glucan in brown algae, laminarin plays a regulator role of the intestinal metabolism through its impacts on mucus structure, intestinal pH, and SCFA formation (Smith et al., 2011; Holdt & Kraan 2011). Polysaccharides show anti-herpetic bioactivity; they are potent as an anticoagulant and decrease low-density lipid (LDL)-cholesterols in rats (hypercholesterolemia); they prevent obesity, large intestine cancer and diabetes; and they have antiviral activities (Migurcova et al., 2012, Matloub et al., 2015, Brown et al., 2012, Karmakar et al., 2010; Vera et al., 2011).
Microalgae cell wall structure is built to protect the cell components and hold its structure and morphology. The cell wall is hard to disrupt and needs aggressive treatment. The structure of the cell wall is a determinant factor in polysaccharide extraction cost. Many techniques have been used to extract polysaccharides from macroalgae. Generally, the sulfated polysaccharides extraction procedure involves a preliminary treatment with a solvent to remove lipids and pigments, followed by proteolysis under acid or alkaline conditions (Fidelis et al., 2014). Recently, physical pre-treatments such as ultrasound sonication and assisted microwave techniques were used instead of chemical pre-treatment to improve polysaccharides yield (Rodriguez-Jasso et al., 2011). Laminarian extraction involve treatments such as grinding and ultrasound assisted extraction (Kadam et al., 2015).
Alginates are extracted from brown macroalgae and can be in the acid or salt form. The acid form is called alginic acid, which is linear polyuronic acid units, and the salt form is a cell wall component constituting 40 to 47% of the dry weight biomass (Draaisma et al., 2013). They are many research report and patents on alginates extraction process from brown macroalgae. However, further detail of any successful commercial extraction process was not reported before (Bothara et al., 2012). Most commercial extractions involve preliminary treatment, grinding, alkaline extraction, calcium or acid precipitation, followed by bleaching and washing steps, and then drying at 42° C. To make the extraction process commercially feasible, they use sodium bicarbonate at pH 10 with grinding and a screen to separate soluble sodium alginate followed by addition of calcium chloride to precipitate sodium alginate in the fibrous form of calcium alginate. Recently, a pilot plant scale extraction was described from the preliminary treatment to the end-product (Hernandez-Carmona et al., 1999; McHugh et al., 2001). The authors used 0.1% formalin solution as overnight preliminary treatment with the ratio of biomass to the solution at 1:9, and then drained and washed with hydrochloridric solution at pH 4 for 15 min. The biomass is heated at 80° C. for 2 hours with constant stirring in a sodium carbonate solution at pH 10 and a ratio of 1:16.6 biomass to the solution, and then it is filtrated. Sodium alginate in suspension is precipitated in 10% calcium chloride. The quantity of required calcium chloride is estimated to 2 parts per 1 part alginate. The precipitate was filtrated using a metal screen (18 mesh). The residual calcium chloride is measured by complexometric titration (Yappert and DuPre, 1997) to optimize the ratio calcium to alginate. Calcium alginate is bleached in sodium hypochlorite solution (5%) and converted to alginic acid with three times washings at pH 1.8 for 15 min each, then the pH is adjusted to 7 using sodium carbonate, and dried at 50° C.
Pigments
The color appearance of algae depends on the type of pigmentation. The primary role of pigments in the photosynthesis process is to absorb visible light and to initiate reactions. Chlorophylls, carotenoids, and phycobilins are the three major groups of pigments. The color changes during the life cycle of crops depending on the content of these pigments. The green color is influenced by the high content of chlorophylls. Yellow and orange color is depending on the content of carotenoids, which are high in microalgae and macroalgae. Phycobilins are dominant in cyanobacteria.
Chlorophylls are known by their greenish color. Chlorophyll a is the primary pigment in the photosynthesis chain and serves as a first electron donor. Chlorophylls b, c, and d are considered accessory pigments. Carotenoids are known for their health benefits, Lutein and zeaxanthin have been reported to reduce the incidence of the age-related macular degeneration (Schalch et al., 2007).
Carotenoids are localized in or attached to the chloroplast membrane. Their main role is to protect the chloroplast membrane components against photo-oxidative damage when there is an excess of solar energy. The antioxidant properties of carotenoids distinguish them from other pigments. Generally, carotenoids are water-insoluble molecules attached to the membrane. Thus their extraction is performed by solvents. The carotenoids are divided based on structure into two classes: carotenes and xanthophylls. Carotenes are hydrocarbons, and xanthophylls are known by their oxygenated functional groups. Since they are hydrocarbons, and therefore contain no oxygen, carotenes are fat-soluble and insoluble in water. In contrast with other carotenoids, xanthophylls contain oxygen and thus are less chemically hydrophobic. Xanthophyll molecules are more polar than carotenes. The major types of carotenoids classes are lutein, β-carotene, canthaxanthin, zeaxanthin, lycopene, and astaxanthin. Astaxanthin antioxidant activity is 10 times higher than β-carotene (Naguib, 2000).
Carotenoids have been used in food, beverages, cosmetics, coloring, and supplements industries. Carotenoids global market is estimated to reach $1.53 Billion by 2021 (Persistence Market Research 2017). Carotenoids have been found in many organisms. Microalgae show a high content of carotenoids and have created a wide interest. Dunaliella salina accumulates β-carotene up to 14% dry weight (DW), and Haematococcus pluialis is rich in astaxanthins (2-3% DW) (Ibañez et al., 2011). The high content of lutein in Chlorella vulgaris had been reported by Lordan and Stanton (2011).
*** Dietary Fiber Health Benefits
Epidemiological and clinical studies demonstrate that diets rich in dietary fiber reduce chronic disease risks and improve individual well-being (Anderson et al., 2009; Bindels et al., 2015; Jiménez-Escrig, et al., 2000). They reported numerous health benefits gains after consuming a diet rich in dietary fibers. Dietary fibers have also been linked with beneficial health effects in gastrointestinal inflammatory disorders and colon cancer prevention (West et al., 2015). A daily intake of the recommended dose of dietary fiber, for example over 20 g/d, can inverse adverse health effects. Other health benefits have also been identified, such as reducing risks of cardiovascular disease, immune system and type 2 diabetes (Stephen et al., 2017). High dietary fiber intake is associated with improvement of glycemic response and insulin sensitivity, and contributes to the overall energy intake management (Nicolucci et al., 2015). Unfortunately, many adverse effects were also reported in individuals who are consuming a diet poor in dietary fiber or taking an inadequate dose of dietary fiber. Adverse effects include high risk of obesity (Tweney et al., 2017), type 2 diabetes (Gulati and Misra, 2017), inflammatory bowel disease (Sheehan et al., 2015), colon cancer (Mehta et al., 2017; Navarro et al., 2016) and cardiovascular disease (Lu et al., 2017).
Dietary guidelines for fiber intake vary and depend on different parameters, including age. Generally, the recommended daily intake range is between 25 g/d and 38 g/d (Stephen et al., 2017). The average daily intake of dietary fibers among the U.S. population ranges between 14.1 g/d and 17.8 g/d, well below the recommended daily intake range (Zhang et al., 2015). The low daily intake of dietary fiber may be associated with many adverse health issues and chronic disease risk factors (Zhang et al., 2015). Survey data show high rates of people in the U.S. population are expected to exhibit symptoms of chronic disease (Dai et al., 2017). Chronic diseases are the leading cause of death in the United States (Seigel et al., 2016).
Dietary fibers are carbohydrate polymers. Their hydrolysis generates free carbohydrate units that are metabolized by cells, such as colonic bacteria. A major component of plant cell walls is carbohydrate polymers including cellulose, hemicellulose, and pectin. Carbohydrate polymers are also extracted from seaweed. Cellulose is the most abundant carbohydrate polymer in land crops and consists of glucose monomer. Cellulose is a water-insoluble polymer; it improves fecal volume and colonic movement where it is partially fermented by gut microbiota (Bishehsari et al., 2018). Hemicellulose polymer consists of pentose and hexose monomers. Pentose includes xylose and arabinose. Hexose includes galactose, glucose, manose, rhamnose, glucuronic and galacturonic acids. Pectin polymer is also formed by pentose and hexose units and known for their health benefits (Kay, 1982). The degree of polymerization of oligosaccharides is between 3 to 10 units. Oligosaccharides are mainly found in fruits and seeds. The most popular oligosaccharides are fructooligosaccharides (FOS), galactooligosaccharides (GOS) and inulin. Their consumption had been reported to be associated with health benefits (Gibson et al., 2017).
Commercial applications and transit time efficiency of dietary fibers are determined by their physical properties. There are two groups of dietary fibers: water-soluble and water-insoluble polysaccharides. Water-insoluble dietary fibers are less fermented or not fermented at all by the colon microbiota. Water-insoluble dietary fibers have a positive role in the digestive system e.g., influencing the food transit time in the small and large intestine and moderating nutrient adsorption. Water-soluble dietary fibers are fermented by the colon microbiota. Water-soluble dietary fibers are often used in the food, beverages, cosmetic, pharmaceutical, and supplement industries. Water-soluble dietary fibers are easy to mix with other ingredients. Water-soluble dietary fibers improve product structure and texture.
The gut (colon) microbiota is an ecosystem of living microorganisms in the human digestive system. The microbiota is a symbiotic interaction between human eukaryotic cells and prokaryotic bacteria in the large intestine. In this symbiotic relationship, the colon is an incubator and fermenter where bacteria find the right temperature and other physical parameters to grow and metabolize non-digested substrates remaining after passing through the small intestine. These non-digested substrates can be carbohydrate, proteins or any other synthesized or biosynthesized chemical component.
Food nutrients which were not digested and absorbed in the small intestine will move to the large intestine (colon) where they will be fermented. Carbohydrate fermentation is a process of converting carbohydrate into end products such as short chain fatty acids (SCFAs), gases, and heat. The major SCFAs are acetic, propionic and butyric acids. Acetate is known by its 2 carbon units, propionates by 3 carbon units, and butyrate by 4 carbon units. Generally, SCFAs are reported to be involved in the gut microbiota energy homeostasis (Rosenbaum et al., 2015). The synthesis of SCFAs is associated with health benefits to the body.
The human colon contains a complex microbiota ecosystem. It was estimated to be 104 bacteria belonging to more than 1000 species (Lozupone et al., 2012). Moreover, the proportion of SCFA content depends on the type of fiber substrate and microbiota (Aguirre et al., 2014). If we want to target specific health benefits or physiological effects, the type of dietary fiber choice is an important parameter. For this purpose, every dietary fiber needs to be characterized and correlated to its impact on colon microbiota composition and metabolism effects. Unfortunately, only a few studies on the effects of each type of dietary fiber have been reported. Yang et al. reported that there is a specific impact for each dietary fiber type on colon microbiota composition and metabolism. Dietary fibers such as pectin, inulin, resistant starch, beta-glucan, arabynoxylan were used in an in vitro study. Fermenting all these dietary fibers is associated with a significant increase of acetate comparatively to propionate and butyrate. Acetate plays a major role in the human body; it serves as a source of energy in peripheral tissues and liver. Moreover, acetate is involved in gluconeogenesis and lipogenesis metabolic pathways as a signaling molecule (Zambell et al., 2003). There is also the differential growth of colonic bacteria. Since most available dietary fibers promote acetate production, there is a need to develop novel dietary fibers that will promote the production of SCFA, especially butyrate. Such dietary fiber will promote and maintain colon microbiota diversity. In this purpose, a microalgal water-soluble dietary fiber is proposed in the present invention.
The study on germ free rate confirmed that SCFAs are essential to colonic cell proliferation and necessary to maintain healthy physiology (Koh et al., 2016, Sakata, 1987). SCFAs are metabolized inside the colon and absorbed and transported in the bloodstream or used by colonic epithelial cells (Macfarlane et al., 2003). Over 95% of SCFAs are absorbed from the colonic lumen (Binder et al., 1989). SCFAs can be considered a significant link between “healthy fiber” and body health benefits (Delcour et al., 2016). SCFAs are preferentially used by colonic mucosa as an energy source. These health benefits of SCFAs are confirmed by many previous reports. Propionate modulates the cholesterol concentration in the blood (Ashraf et al., 2017). Butyrate is a major source of energy in the distal gut for colonocytes and enterocytes (Donohoe et al., 2011), and it protects colonic mucosa and stimulates epithelial cell proliferation (Hamer et al., 2008). These effects improve barrier functions in the distal region of the large intestine (Kelly et al, 2015). It was confirmed that the decrease of bacteria producing butyrate is inversely associated with many colonic diseases including inflammatory bowel disease (Machiels et al., 2013).
An important parameter that can distinguish between dietary fiber groups is the fermenting behavior of dietary fibers. A slowly fermentable dietary fiber is highly desired and is associated with many health benefits. In the gut, a slow fermenting dietary fiber generates less gas than a rapidly fermenting dietary fiber.
Rapidly fermenting dietary fiber is not preferred. The majority, if it is not all, of rapidly fermenting dietary fiber is fermented in the proximal area of the colon. The fermentation rate in the proximal area is enough to generate a high volume of gas, causing bloating and discomfort. The distal region of the colon is almost deprived of dietary fiber. This shortage of carbohydrate in the distal area is generally compensated by proteins. The fermentation of proteins by colon bacteria in the distal area generates toxic metabolites, such as phenols and ammonia.
In contrast, slowly fermented dietary fibers are not totally fermented in the proximal region of the colon. Slowly fermented dietary fibers are fermented along with the colon, creating an environment of detoxification, and producing SCFAs that are adsorbed in both proximal and distal colon regions. Fermentation of slowly fermented dietary fibers throughout the colon can reduce colonic diseases risks and improve colon health.
Most commercially available dietary fibers are rapidly fermenting, such as fructooligosaccharides (FOS). In some cases, the commercially available dietary fibers are poorly fermented such as pectin, and β-glucan. Other dietary fibers are poorly fermenting or non-fermenting such as whole or debris of cell wall, cellulose, etc. The ideal characteristics of dietary fiber are: slowly fermenting, water-soluble, fully metabolized by colon microbiota, and generates bioactive components such as SCFA (especially butyrate).
Cereals, fruits, and vegetables are the main source of dietary fiber in the human diet. There is global population growth and is expected to reach 9.3 billion by 2050. Land crops may not be able to respond to the global food demand in the future. Moreover, dietary fibers from land crops need to be modified to reach the ideal characteristics. There is a need to find or develop other biomass sources for dietary fiber production with these ideal characteristics.
Marine crops may be a sustainable alternative to land crops. Seaweed biomass has already shown the capability to provides polysaccharides (fibers) and other high-value chemicals. Microalgae can be sustainable biomass that is a potential source of dietary fiber and many high-value products. Microalgae are photosynthetic organisms. Microalgae convert carbon dioxide, CO2, into organic molecules using solar energy. Microalgae can grow on any land and use seawater. Microalgae can grow where no other land crop can grow. Microalgae may be a sustainable alternative to classic biomass sources. The daily intake of microalgal dietary fibers may be associated with health benefits that many classic dietary fibers do not provide.
There are previous inventions reporting the role of dietary fiber on the colonic health, especially bowel health and gastrointestinal inflammation. Some of them reported the role of polysaccharides in colonic health. These polysaccharides were extracted from cereals (Hamaker et al. 2014) or on resistant starch (Cummings et al., 1996) and described below.
Related Patents
The U.S. Published Patent Application No. 2015/0010,672A1 by Hamaker et al. and published on Sep. 19, 2014, teaches a slowly fermentable soluble dietary fiber. Fermentation of treated bran or hydrolysate product resulted in about 50 percent to about 93 percent by weight arabinoxylans. The bran was selected from the group consisting of corn, wheat, rice, sorghum, and any combination thereof. The study found slow fermentation of dietary fiber is associated with higher level of butyrate production than FOS.
The U.S. Published Patent Application No. 2015/0359,836A1 by Israelsen and published on Aug. 25, 2015, teaches using both probiotic bacteria and fermented cereal as a treatment for inflammatory bowel diseases, irritable bowel syndrome, and other gastrointestinal disorders. The treatment strategy alleviated the symptoms of inflammatory bowel diseases regardless of a mild, moderate, or severe stage of the disease.
The U.S. Pat. No. 9,579,340A1 by Ritter et al. and issued on Feb. 28, 2017, teaches a prebiotic formulation for treating symptoms associated with lactose intolerance and for overall improvement in gastrointestinal health. The prebiotic is mainly a galactooligosaccharide (GOS).
The U.S. Pat. No. 9,668,992 B1 by Cahan et al., and issued on Jun. 6, 2017, teaches the SCFA composition in the colon. It also teaches composition for treating the colon with a core including at least one SCFA composition or a pharmaceutically acceptable salt or ester thereof.
The U.S. Pat. No. 7,700,139, by Bird et al., issued Apr. 20, 010, teaches a resistant starch that produced a high level of butyrate during fermentation (Bird et al., 2010; U.S. Pat. No. 7,700,139). Unfortunately, the composition does not have the appropriate and necessary physical properties to have many commercial applications in food, beverages, etc.